Just did compression test pissssed!!!!!

[2GFWDbeast]

Had a shop do my engine build for me. They told me not to do any hard driving for at least 500 miles. So far i only have 199 miles on it, and its been about a month. I decided to do a compression test and it was 160 128 130 160 cause i noticed my vacuum at idle was little on the low side.

I have Je pistons 9.5:1. My vacuum is at 8 in/hg at idle. I do have hks 272 cams. Could it be that piston 2 and 3 haven't seated yet or do i need to goto the shop and bi*** at them, cause they messed something up.

 

[3kgt2nv]

rings didnt seat. if its a turbo car it should have been being boosted since day one and use an alternating load pattern. even allowing a car with new rings to idle for too long with no load can cause them to seat improperly.

 

[2GFWDbeast]

iv boosted it a little bit nothing major. its seen 10psi of boost at the most. everyday i drive it i boost it a little bit, but like i said no more then 10psi.

 

[GRAVEDIGGER]

I would like to see you drive it a little more and maybe check it again around that 500 mile mark before you panic and bi*** about it. Have you attempted to break in the motor? If it were mine I would be running about 12-15psi if possible and not really going WOT. I would try to do some steady boosting at say 3/4 throttle and then go from boost to vacuum and let it decel. Do that kind of driving as much as possibe for a couple more hundred miles and see where you're at. Hopefully 2-3 will come up. If not, then you will have something to bi*** about.

 

[3kgt2nv]

its the constant you want to avoid. you need stop and go traffic and fluctuating rpms with different loads on the motor. try beating on it and see if it improves any.

I was told by a shop that builds alot of high power motors the way they break them in is.

start and idle for about 2 mins. change oil
drive around town boosting medium in stop and go traffic for about 20 miles
put it on the dyno and push it hard.

they dont have a lot of low compression issues

 

[greenydsm]

let the engine slow you down as much as possible. Take it out on back roads. 3/4 throttle up to 5kish then just have the engine brake to slow you down. Maybe put a capful of oil in each cylinder to help a little bit. When I rebuilt my one engine it was a little low, after i did these it helped alot!

 

[2GbTalonGuy]

Since when are you supposed to baby an engine until it is broken in?

You want to what greeny said and see if compression improves. It will probably still be low because the most important part of a break in procedure is within the first 20 miles.

 

[2GFWDbeast]

i didnt know any of this being my first engine build, and being that i spent almost 5000 bucks i didnt want to do anything wrong so iv been pretty much babying it. , and doing what the machine shop told me to do. the shop i brought it to has been in business for 60 years, and builds big block race motors. So i figured they know what there talking about.

 

[gofer]

Do they build boosted race engines?

- More Power/Less Wear Engine Break-In
- AMS Performance Engine Break-In​

 

[2GFWDbeast]

ehhh not to my knowledge. i have seen a few boosted buicks in there tho. They have a guy there that specializes in dsm's name matt white.

 

[Talonious]

I wouldn't check your compression till about 1000 miles. Just drive it like a normal car, while shifting more often and applying gas once in a while. Then every minute or two just do a nice pull. Get some load on the motor and you'll be fine to check compression then.

Also dont use crappy rental compression testers, buy an actron it's decently accurate.

 

[Tanro]

You really need to do the Motoman breaking method on most cars these days.

You basically accelerate spiritedly (not floord) and then cost down to around 30 and repeat. Drive with stock boost levels, dont be afraid of boost.

The reason you engine brake is that the intense vacuum helps pull the oil off the cylinder walls. Babying it during breaking will #### it up.

 

[2GFWDbeast]

so do you think iv done damage to the point where it messed up and need new rings or with the 199 miles im still in the clear and just need to drive it a little harder and hope the compression comes up in 2 and 3.

 

[Imback]

If you didn't get the rings seated within the first 20 miles i don't think there is much you can do to get the compression back up. I may be wrong though as am not an engine builder. I used ams's as well as motomans break in procedure. i was boosting 20psi the first time i got the car running and letting it decelerate by it's self as well.

 

[Talonious]

so do you think iv done damage to the point where it messed up and need new rings or with the 199 miles im still in the clear and just need to drive it a little harder and hope the compression comes up in 2 and 3.

No, I drove my newly built engine with a bad front o2 sensor. First 500 miles on my engine were with idle/ cruising afr's around 12, while babying it because it was running so rich.

I then fixed my fuel trims, and since the past 2 weeks of driving all over the state, about 1000 hard miles, my compression pulled 205-205-205-205. (9:1 pistons)

I think your good still, just don't baby it at all. If it does blow up, it was horribly built in the first place.

 

[2GFWDbeast]

is the break in period different on a n/a muscle car then it is on a boosted car?

 

[Talonious]

Not really, you should put load on any motor for its breakin..Mid-WOT pull, then let it engine brake.

Turbocharged engines have more compression while in boost than an N/A would and to a point the pressure of a Turbo engine's combustion is way higher, which throws the rings to the wall and makes them seat.

Anyone that tells you to not run boost doesn't know that it's better for break-in, or they just are used to building N/A v8's.

 

[2GFWDbeast]

No, I drove my newly built engine with a bad front o2 sensor. First 500 miles on my engine were with idle/ cruising afr's around 12, while babying it because it was running so rich.

I then fixed my fuel trims, and since the past 2 weeks of driving all over the state, about 1000 hard miles, my compression pulled 205-205-205-205. (9:1 pistons)

I think your good still, just don't baby it at all. If it does blow up, it was horribly built in the first place.

what was the compression at 500 miles?

 

[Talonious]

what was the compression at 500 miles?

140-130-130-140

 

[2GFWDbeast]

140-130-130-140

whaaa damn ok ok. well maybe i should start driving it a little harder then, and hope the numbers increase.

 

[staztrx250]

whaaa damn ok ok. well maybe i should start driving it a little harder then, and hope the numbers increase.

seating rings 101 drive the bi*** like you stole it.


well don't beat the piss out of it but yeah like everyone said constants ins your enemy just drive erratic!!!

oh one question you didn't put synthetic in it did you?

 

[Talonious]

Yeah, when I was on the highway going to dayton I just ended up doing variations of 3rd, 4th, 5th load pulls. Nobody got too mad at me because I would just pull up to 85 and engine break to 65 and continue that.

That is if you highway drive often.

 

[2GFWDbeast]

no i used joe gibbs break in oil.

 

[2GFWDbeast]

UPDATE: Drove the car 12 more miles today, and did 1/2 to close to 3/4 throttle runs with it and let motor slow its self down. Boosted it to about 15psi. Did a compression test again and now its 160 145 145 160 so a 15psi improvement from yesterday on the 2 middle cylinders.

Could it be that i just haven't drove it enough yet. total mileage 228 since the engine build.

Should i not jump the gun, and goto the shop that built my motor and complain that the compression is low. Should i just wait till I get 500 miles on it, and change out the oil then re-check the compression. again

 

[3kgt2nv]

I would keep doing what your doing and work in some wot runs to see if it does the job.